Showing papers on "Blade pitch published in 1984"

Blade pitch varying means

Abstract: Blade pitch varying means for use in a gas turbine engine are disclosed. The blade pitch varying means may be used on an engine with a single row or two counterrotating rows of variable pitch blades which are disposed outwardly from an annular gas flowpath and which are connected with a rotating airfoil within the flowpath. The blade pitch varying means comprise actuation means, bearing means, and gearing means. The actuation means are in a nonrotating reference frame disposed inwardly from the flowpath and deliver an axial force. The bearing means transmit the axial force from the nonrotating into a rotating reference frame which contains both the propulsor blade and the airfoil in the gas flowpath. The gearing means are located in the rotating reference frame and convert the axial force into a force for varying the blade pitch.

Blade pitch control of a wind turbine

Abstract: A control system for adjusting the pitch of variable-pitch angle blades in a wind turbine for generating electric power maintains the control signal for the variable-pitch angle blades above a minimum level representing the minimum desired angle of the variable-pitch blades. The control system includes a subtractor for generating a difference signal; a device for generating from the difference signal a first blade control signal greater than a minimum level, from a device for generating a second blade control signal greater than a minimum level, from first blade control signal and the difference signal; a device for generating a third blade control signal for adjusting the pitch of variable-pitch angle blades, from second blade control signal and power rate signal. All devices include limiters which limit their respective output signals to a minimum level representing a preset minimum blade angle.

Devices which may be borne in air and on devices applicable therein

Abstract: A rotor having airfoil section shaped blades is set into a fluid stream. Over a connection or transmission means a propeller is connected to the rotor. The fluid stream whereinto the rotor is set gives airflow energy to the rotor and revolves the rotor. The propeller is driven by the rotor over the connection or transmission means. Since the propeller is revolved by the rotor in the fluid stream, the propeller provides a thrust. The thrust may be used to lift a weight or to drive a member. A suitable application of the arrangement is, for example, to transform a multibladed helicopter into a gliding craft which descends under a gliding angle towards the surface of the earth when the helicopter has a complete engine failure. Auto-rotation accidents can thereby be prevented. The device is also applicable to drive a vehicle or to lift a weight. Variable means can be applied to obtain variable thrusts in flying craft to improve their efficiencies or change from one flight system to another flight system. In other embodiments several novel concepts for air-borne craft are provided which include emergency landing devices, retractable and extendable or relation varifying devices for wings or propellers.

Method and apparatus for controlling windmill blade pitch

Abstract: In order to control the turbine speed of a windmill employed for power generation, the pitch of the turbine blades is based on a dual-deadband control strategy. If the current turbine speed is determined to be outside of a relatively wide deadband, action is taken to correct the speed by changing blade pitch accordingly. If the current speed is not outside of the relatively wide deadband, then the average of the turbine speed over a recent interval is compared with a relatively narrow deadband within the wider deadband. Action is then taken to change the blade pitch if the average speed is outside the narrow deadband. In this way, wide excursions of turbine speed are corrected promptly, but the frequency of control actions is minimized by requiring only the average speed to be kept within tight limits.

Helicopter individual-blade-control and its applications

Abstract: A new, advanced type of active control for helicopters and its applications are described. The system, based on previously developed M.I.T. Individual-Blade-Control hardware, employs blade-mounted accelerometers to sense blade motion and feeds back information to control blade pitch in such a manner as to reduce the response of selected blade modes. A linear model of the blade and control system dynamics is used to give guidance in the design process as well as to aid in analysis of experimental results. System performance in wind tunnel tests is described, and evidence is given of the system's ability to provide substantial reduction in blade modal responses, including blade bending vibration.

Propeller pitch change actuation system

Abstract: A propeller pitch change actuation system comprises an input actuator (230) driving a ball screw (200). Operation of the ball screw rotates a torque tube (140) about the longitudinal axis thereof to drive a screw 145 and control valve 120 which controls the pressurization of pitch change actuator (87). Actuator (87) is supplied with hydraulic fluid through the interior of the torque tube.

Position and control system for helicopter blade actuation

Abstract: Mecanisme de commande et de positionnement des pales d'un helicoptere comportant un arbre de rotor creux (14) pour monter une pluralite de pales de rotor (22) tout en permettant le reglage du pas. control mechanism and positioning the blades of a helicopter having a hollow rotor shaft (14) for mounting a plurality of rotor blades (22) while allowing the pitch adjustment. Un arbre de commande (28) est dispose a l'interieur de l'arbre du rotor, il peut tourner par rapport a celui-ci et est associe a des verins (20) pour les pales, si bien que le pas des pales est modifie lorsque l'arbre de commande tourne par rapport a l'arbre du rotor. A control shaft (28) is disposed inside the rotor shaft, it can rotate relative thereto and is associated with the jacks (20) for the blades so that the pitch of the blades is modified when the control shaft rotates relative to the rotor shaft. Un montage d'engrenage planetaire (44) relie l'arbre de commande a une source d'energie fixee au fuselage de l'helicoptere (10) et, lorsque une entree du montage d'engrenage planetaire est au repos, l'arbre de commande tourne dans la meme direction et a la meme vitesse que l'arbre du rotor afin de maintenir un pas desire. A planetary gear assembly (44) connects the drive shaft to a power source attached to the fuselage of the helicopter (10) and, when an input of the planetary gear assembly is at rest, the shaft command rotates in the same direction and at the same speed as the rotor shaft to maintain a desired pitch. Reciproquement, lorsqu'une entree est placee sur le systeme d'engrenage planetaire, il se produit une rotation relative entre l'arbre de commande et l'arbre du rotor afin de permettre le reglage desire du pas des pales. Conversely, when an entry is placed on the planetary gear system, there occurs a relative rotation between the drive shaft and the rotor shaft to permit the desired adjustment of blade pitch. Le systeme permet de tirer des signaux de retour de positionnement precis des pales d'un dispositif de retour monte de maniere stationnaire sur le fuselage. The system allows to draw precise positioning feedback signals of the blades of a feedback device mounted stationary on the fuselage.

Double propeller drive for boats

Abstract: A boat propeller drive with double, counter-rotating propellers is distinguished by the after propeller having one more blade than the fore propeller as well as a smaller diameter than the fore propeller.

Variable camber tandem blade bow for turbomachines

Abstract: Multiple flat-plate blade rows of pitch adjustable blades are offset mounted in a manner such that when flat-plate blades in adjacent rows are aligned at a specific pitch setting, respective flat-plate blades of the adjacent rows nearly mate. The offset between the flat-plate blade rows functions to produce unequal pitch angle settings of the blades of adjacent rows which, in turn, function to produce the result that the respective flat-plate blades which nearly mate, in combination, produce a blade configuration which has an effective camber.

Windmill with controller for controlling rotor RPM

Abstract: A windmill construction embodying an improved arrangement for driving a load through a centrifugal clutch and for adjusting the pitch angle of the blades. The adjusting mechanism is responsive to speed so as to increase the pitch angle as the speed increases and further incorporates a latch mechanism for latching the blades in a maximum feathering pitch angle and for introducing a hysteresis effect into the mechanism.

Effect of angle of attack on rotor trailing-edge noise

Abstract: Previous analyses of boundary layer trailing edge noise for large rotors have used zero blade angle of attack as input data. Attention is presently given to the important effects of blade angle of attack changes on rotor trailing edge noise in the case of a UH-1 helicopter. The primary effect is in the low to mid-frequency range, where noise level increases with angle of attack.

Blade pitch changing mechanism

Abstract: Overspeed conditions in a ram air turbine are eliminated through a novel blade pitching mechanism. The mechanism includes a rotatable shaft with a hub mounted thereon for rotation therewith. The hub rotatably mounts at least one blade and a hollow blade pitch control shaft extends generally concentrically about the rotatable shaft and is mounted for reciprocating movement in a path toward and away from the hub. A reciprocating to rotary motion converting mechanism interconnects the control shaft and the blade so that the pitch of the blade can be controlled by controlling the position of the control shaft in the path. A first motor is provided for incrementally moving the control shaft within the path and a second motor is provided for rapidly moving the control shaft within the path to a position therein corresponding to a feathered position of the blades.

Hub-mounted actuators for blade pitch collective control

Abstract: Blade collective pitch control is provided for a rotor system by rotary actuators located between adjacent blades. Each actuator is connected to the leading edge of one adjacent blade and the trailing edge of the other adjacent blade.

Development and evaluation of a generic active helicopter vibration controller

Abstract: A computerized generic active controller is developed, which alleviates helicopter vibration by closed-loop implementation of higher harmonic control (HHC). In the system, the higher harmonic blade pitch is input through a standard helicopter swashplate; for a four-blade helicopter rotor the 4/rev vibration in the rotorcraft is minimized by inducing cyclic pitch motions at 3, 4, and 5/rev in the rotating system. The controller employs the deterministic, cautious, and dual control approaches and two linear system models (local and global), as well as several methods of limiting control. Based on model testing, performed at moderate to high values of forward velocity and rotor thrust, reductions in the rotor test apparatus vibration from 75 to 95 percent are predicted, with HHC pitch amplitudes of less than one degree. Good performance is also noted for short-duration maneuvers.

Propeller device for a ship

Abstract: A propeller device for a ship rotates 360° and may be raised when it is not in use. The transmission system of the propeller device includes a drive shaft for the propeller device, which is placed in the upper part of such propeller device. The shaft is driven by the shaft of the engine and transmits rotation via an upper angular gearbox to a vertical shaft and a lower angular gearbox to a propeller shaft at the bottom part of the propeller device. A coupling is fitted between the drive shaft of the propeller device and the engine shaft rotating same. A coupling member of the coupling permits the propeller device to be uncoupled from the engine and to be displaced in the axial direction, so that the propeller device may be raised.

Aircraft propeller with blade pitch adjustment for feather and reverse positions

Abstract: A propeller hub supports a plurality of adjustable pitch propeller blades which are rotated by a hydraulic cylinder and control system between a feather position and a reverse position through low and high pitch positions. The reverse pitch position is precisely set by axially adjusting a tubular sleeve threadably connected to the hydraulic cylinder and having an inner end surface forming a stop for the piston within the cylinder. The feather position is precisely set by axially adjusting lock nuts mounted on a threaded end portion of the piston rod projecting forwardly beyond the forward end of the sleeve. The hub also encloses feedback control rods which carry externally adjustable nuts providing for pilot control of the blade pitch into the reverse position.

Higher harmonic control for rotary wing aircraft

Abstract: Higher Harmonic Control reduces helicopter airframe vibration through the exercise of rotor blade pitch control at frequencies that are higher harmonics of rotor rotation Analysis wind tunnel tests and flight tests of this technology with an OH-6A helicopter have led to vibration reduction levels of the order of more than 80 percent Blade feathering capability at rotor speed harmonics other than the first also promises the improvement of such rotor characteristics as acoustics, aerodynamic efficiency and ground resonance

On the Design of Horizontal Axis Two-Bladed Hinged Wind Turbines

Abstract: Hinged two-bladed wind turbines are not necessarily free of disturbing vibrations. The combination of elastic or built-in blade coning with blade flapping about a conventional teeter hinge produces periodic blade angular velocity variations in the blade tip path plane with associated vibrations and dynamic loads. The paper discusses and evaluates various hinge configurations for two-bladed rotors and shows why the conventional teeter hinge leads to nonuniform blade angular velocity in the blade tip path plane. The solution to this problem adopted for two-bladed helicopter rotors, though complex, could be of interest for large wind turbines. A much simpler solution, calling for the suppression of blade flapping by passive blade cyclic pitch variation produced by a strong negative pitch-flap coupling, was found to be practical for upwind tail vane stabilized two-bladed wind turbines.

Aileron controls for wind turbine applications

Abstract: Horizontal axis wind turbines which utilize partial or full variable blade pitch to regulate rotor speed were examined. The weight and costs of these systems indicated a need for alternate methods of rotor control. Aileron control is an alternative which has potential to meet this need. Aileron control rotors were tested on the Mod-O wind turbine to determine their power regulation and shutdown characteristics. Test results for a 20 and 38% chord aileron control rotor are presented. Test is shown that aileron control is a viable method for safety for safely controlling rotor speed, following a loss of general load.

Application of an optimization method to high performance propeller designs

Abstract: The application of an optimization method to determine the propeller blade twist distribution which maximizes propeller efficiency is presented. The optimization employs a previously developed method which has been improved to include the effects of blade drag, camber and thickness. Before the optimization portion of the computer code is used, comparisons of calculated propeller efficiencies and power coefficients are made with experimental data for one NACA propeller at Mach numbers in the range of 0.24 to 0.50 and another NACA propeller at a Mach number of 0.71 to validate the propeller aerodynamic analysis portion of the computer code. Then comparisons of calculated propeller efficiencies for the optimized and the original propellers show the benefits of the optimization method in improving propeller performance. This method can be applied to the aerodynamic design of propellers having straight, swept, or nonplanar propeller blades.

Helicopter blade pitch adjusting system

Abstract: A helicopter blade positioning mechanism provides collective and cyclic pitch angle adjustment of the blades independently This mechanism is all enclosed within the blade driving axle The pitch angle of each blade is adjusted collectively and cyclicly by direct action on and within the blade hub No other linkage is required between the blade and the blade pitch actuation means The cyclic pitch adjustment of each blade is obtained either by a rotation imparted to the whole blade body or by twisting the blade, depending upon the mechanism configuration used In both cases, the cyclic pitch variations are superimposed on the collective pitch setting, vary sinusoidally as the blades gyrate around their vertical axis of gyration, one full pitch variation cycle for each full gyration of the blades This mechanism plays the role and replaces the well known swash-plate/linkage arrangement used on most helicopters

Propeller noise measurements inf DNW on the fuselage of a twin engine aircraft model

Abstract: Results of sound pressure measurements on the fuselage wall of a twin engine propeller driven model are presented The tests were carried out in the German-Dutch low speed wind tunnel DNW in the Netherlands The model was equipped with either metallic propeller blades or composite blades The propeller diameter was 0762 m Six microphones were installed in the area of minimum propeller tip clearance The experimental data obtained at several wind speeds, angles of attack and propeller rotational speeds show encouraging comparisons with free field and installed noise predictions derived using theoretical and/or empirical methods

Helicopter stall alleviation using individual-blade control

Abstract: A new, advanced type of active control for helicopters and its application to the solution of rotor aerodynamic and aeroelastic problems is described. Each blade is individually controlled in the rotating frame over a wide range of frequencies up to the sixth harmonic of rotor speed. The paper describes the design of a system controlling retreating blade stall, and the testing of the system on a model rotor in the wind tunnel. The control inputs considered are higher harmonic blade pitch changes at 2P and 3P, of amplitude and phase such that rotor loading is increased in the fore and aft portions of the rotor disk while rotor loading is reduced on the lateral portions. In this manner retreating blade stall may be alleviated, with corresponding reduction in rotor power requirements and vibration.

An advanced pitch change mechanism incorporating a hybrid traction drive

Abstract: A design of a propeller pitch control mechanism is described that meets the demanding requirements of a high-power, advanced turboprop. In this application, blade twisting moment torque can be comparable to that of the main reduction gearbox output: precise pitch control, reliability and compactness are all at a premium. A key element in the design is a compact, high-ratio hybrid traction drive which offers low torque ripple and high torsional stiffness. The traction drive couples a high speed electric motor/alternator unit to a ball screw that actuates the blade control links. The technical merits of this arrangement and the performance characteristics of the traction drive are discussed. Comparisons are made to the more conventional pitch control mechanisms.

Safety device for wind force prime mover

Abstract: PURPOSE:To improve safety by disengaging a lock mechanism to provide blade pitch not producing turning force without any other power such as electricity, hydraulic pressure, etc. and stop the rotation so that the blade is not returned to the original position by its own force when the rotation of a wind mill is speeded up excessively by gust or the like. CONSTITUTION:When blade pitch control cannot follow abrupt increase of wind speed due to typhoon, gust, etc. and the rotation of blade is abruptly increased to dangerous rotational frequency, rollers 18 interlocked with each other are expanded to the outer periphery and disengaged from a concave groove 15a in a cylinder head 15 by the centrifugal force of weights 16. When a lock mechanism is released, a movable plate 8 is forcibly attracted toward a disk 6 by a pitch spring 12 and air force of wind mill blade 4, while providing the blade pitch of the wind mill blade 4 so as not producing turning force through a control shaft 7, connecting rod 10 and blade shaft arm 11 to stop the wind mill.

Comparison of model helicopter rotor primary and secondary blade/vortex interaction blade slap

Abstract: A study of the relative importance of blade/vortex interactions which occur on the retreating side of a model helicopter rotor disk is described Some of the salient characteristics of this phenomenon are presented and discussed It is shown that the resulting secondary blade slap may be of equal or greater intensity than the ad vancing side (primary) blade slap Instrumented model helicopter rotor data are presented which reveal the nature of the retreating blade/vortex interaction The importance of secondary blade slap as it applies to predictive techniques or approaches is discussed When secondary blade slap occurs it acts to enlarge the window of operating conditions for which blade slap exists Nomenclature B = number of blades c =chord CT = thrust coefficient thrust/pIIK2 (ttR)2 CT/a = blade loading R = rotor radius V = tunnel speed x/c = nondimensional chordwise position ots = shaft angle Os = pitch at tip =0T A = vortex/blade interaction angle fj, = advance ratio V/SIR p = density of air a = rotor solidity Bc/HR Q = angular velocity

Adjustable pitch propeller for ship's propulsion

Abstract: The adjustable pitch propeller has an adjusting mechanism (15, 23, 91) for adjusting the individual propeller blades (7). The adjusting mechanism (15, 23, 91) contains a correction motor (45, 80) for each propeller blade (7) with a correction mechanism (28, 32, 33, 70) for the cyclical adjustment of the angle of incidence (W) of the relevant propeller blade (7) under the influence of a control device (S).

Shutdown characteristics of the Mod-O wind turbine with aileron controls

Abstract: Horizontal-axis wind turbines utilize partial or full variable blade pitch to regulate rotor speed. The weight and costs of these systems indicated a need for alternate methods of rotor control. Aileron control is an alternative which has potential to meet this need. The NASA Lewis Research Center has been experimentally testing aileron control rotors on the Mod-U wind turbine to determine their power regulation and shutdown characteristics. Experimental and analytical shutdown test results are presented for a 38 percent chord aileron-control rotor. These results indicated that the 38 percent chord ailerons provided overspeed protection over the entire Mod-O operational windspeed range, and had a no-load equilibrium tip speed ratio of 1.9. Thus, the 38 percent chord ailerons had much improved aerodynamic braking capability when compared with the first aileron-control rotor having 20 percent chord ailerons.

Application of an adaptive blade control algorithm to a gust alleviation system

Abstract: The feasibility of an adaptive control system designed to alleviate helicopter gust induced vibration was analytically investigated for an articulated rotor system. This control system is based on discrete optimal control theory, and is composed of a set of measurements (oscillatory hub forces and moments), an identification system using a Kalman filter, a control system based on the minimization of the quadratic performance function, and a simulation system of the helicopter rotor. The gust models are step and sinusoidal vertical gusts. Control inputs are selected at the gust frequency, subharmonic frequency, and superharmonic frequency, and are superimposed on the basic collective and cyclic control inputs. The response to be reduced is selected to be that at the gust frequency because this is the dominant response compared with sub- and superharmonics. Numerical calculations show that the adaptive blade pitch control algorithm satisfactorily alleviates the hub gust response. Almost 100% reduction of the perturbation thrust response to a step gust and more than 50% reduction to a sinusoidal gust are achieved in the numerical simulations.

Remote control apparatus for variable pitch propeller

Abstract: PURPOSE:To make it possible to carry out a cruise at a minimum fuel consumption by setting the load of a main engine in accordance with a set ship speed and an actual ship speed and by controlling the corresponding blade angle with the use of a main engine set torque computing section, a load control section and a blade angle setting section, independently of the control of rotational speed. CONSTITUTION:Upon the control of a combinator by a push button 10, the rotational speed of a governor 18 is set with a setting signal LC by a control lever 3 through a rotational speed setting section 15 while an actuator 21 is operated through a blade angle setting section 20. Upon exceeding an allowable torque limit the blade angle is decreased with a signal from a overload protection control section 23. Upon the control of load, a load signal LL from the lever 3 is delivered to a main engine set torque computing section 24 where a set torque RS is obtained in accordance with a set rotational speed NS, and the set torque RS is compared with an actual torque RA in a load control section 25 which delivers a signal to the blade pitch setting section 20. Further, upon the control of ship speed a ship speed control section 26 sets the load LL in accordance with an actual ship speed VA and a set ship speed VS. At this stage, the driving point is changed by means of a rotational speed changing switch 13 so that the fuel consumption is calculated, thereby a cruise at a minimum fuel consumption may be made by carrying out the operation at its minimum driving point.